优化更新代码，添加界面功能并整合

WPFluent/Controls/TitleBar/IThemeControl.cs

@@ -0,0 +1,15 @@
+
+
+
+namespace WPFluent.Controls;
+
+/// <summary>
+/// Control changing its properties or appearance depending on the theme.
+/// </summary>
+public interface IThemeControl
+{
+    /// <summary>
+    /// Gets the theme that is currently set.
+    /// </summary>
+    public Appearance.ApplicationTheme ApplicationTheme { get; }
+}